"What has happened is a complete failure. It is very serious. It was in breach of the law and exposed Sweden and Swedish citizens to harm," Löfven said at a press conference in Stockholm, The Local reported.

The Swedish Transportation Agency (STA) has since set up a Q&A section on the incident. The agency said since first discovering the breach in 2015, it has taken actions to improve security. "All equipment, programs and data are in Sweden and have always been in Sweden. All data storage management is handled by registered and authorised personnel in Sweden from June 2016," the STA said. The agency added that it saw no indication that "any data has been spread incorrectly".

However, the process of securing the leak is still on. "The work is technically complicated and comprehensive but should be remedied by the autumn of 2017," the STA said.

Following discovery of the incident, the STA's director general, Maria Agren, was quietly dismissed in January. It was reportedly determined that Agren bypassed laws to speed up data outsourcing and was fined 70,000 Swedish krona ($8,500, £6,500), roughly half a month's salary, as punishment.

The STA's new director general, Jonas Bjelfvenstam, has said the authorities are working to ensure that such incidents are not repeated. "I take this seriously and action has been taken. Obviously, we as an authority must comply with the laws, regulations and security requirements that apply in our area of activity. We are doing everything we can to avoid such a situation in the future," he said.

It still remains unclear as to how many people were affected by the data leak.